Suspension tie rods are used in a wide variety of applications to support a component from a structural member. Commonly, an elastomeric isolator is used with the suspension tie rod to improve noise attenuation. The elastomeric isolator can be incorporated into the suspension tie rod in the form of an elastomeric tie rod end, or used in a terminating structure in the form of an elastomeric cartridge. Both the elastomeric tie rod end and elastomeric cartridge include a housing surrounding an annular elastomeric isolator disposed about an inner metal sleeve defining a bore for receiving a pin or bolt for attaching a support lug to the tie rod end or cartridge. The housing of the elastomeric tie rod end includes a threaded section for direct attachment to the suspension tie rod. The housing for the elastomeric cartridge is cylindrical, and is typically inserted into the terminating structure and is swaged in place. The elastomeric isolator serves to dampen vibration and attenuate noise, but also must be capable of carrying a load imposed by the supported component.
For example, suspension tie rods are commonly used on commercial passenger aircraft to support overhead stowage bins from the superstructure of the aircraft fuselage. U.S. Pat. No. 6,874,731 discloses a modular overhead stowage bin system for an aircraft passenger cabin. In a wide body, multi-aisle aircraft, the overhead stowage bins include outboard stowage bins positioned above the right and left side seats of the aircraft and inboard stowage bins positioned above the center seats. The overhead stowage bin compartments are readily assessable to passengers to open the bins to stow and remove carry-on luggage, packages, coats and the like when standing in the passenger aisles. As illustrated in this patent, each of the overhead stowage bins is supported from structural supports coupled to the fuselage framework by means of suspension tie rods.
In conventional systems, each suspension tie rod connects to and extends between one of the structural supports and a respective mounting lug coupled to the framework of the stowage bin it supports. Each of the suspension tie rods supporting a stowage bin includes a tie rod end having at its distal end an outer metal sleeve defining a cylindrical socket in which is coaxially disposed an inner cylindrical metal sleeve. The tie rod ends are commonly all metal and incorporate a spherical bearing. When noise attenuation is desired, an elastomeric tie rod end can replace the all-metal tie rod end, or an elastomeric cartridge isolator may be added to a terminating structure. In both the elastomeric tie rod end and elastomeric cartridge, a generally cylindrical elastomeric annular body, commonly referred to as an isolator, is disposed within the annulus formed between the two metal sleeves. The inner metal sleeve defines an axially extending central bore for receiving a mounting bolt for attaching the tie rod end to a support bracket or lug that is coupled to the framework of the stowage bin supported thereon.
In conventional practice, the elastomeric body, in addition to dampening vibrations, is made of an elastomer material having a selected noise attenuation characteristic. In addition, the elastomeric body functions to carry the load imposed by the weight of the supported stowage bin to the tie rod end. However, in designing conventional elastomeric isolators having a generally cylindrical form, a trade-off must be made when selecting the elastomer material to be used in balancing the need for greater noise attenuation while maintaining adequate load carrying capability. Elastomer materials having a low stiffness characteristically have excellent noise attenuation capability, but relatively poorer load carrying ability. Conversely, elastomer materials having a high stiffness characteristically have relatively good load carrying ability, but relatively poorer noise attenuation capability. Consequently, the need exists for an elastomeric isolator that has both a relatively high noise attenuation characteristic and a relatively good load carrying ability.